Method of implanting an intervertebral spacer

ABSTRACT

An intervertebral spacer adapted for implanting between adjacent vertebral bodies of a human spine as a load-bearing replacement for a spinal disc. The spacing member includes an external, non-porous, concavo-convex contour with respect to one dimension of said spacing member. The spacing member is preferably constructed from a rigid, non-resilient load-bearing material that is incapable of elastic deformation. The spacing member is inserted with the aid of a sheathed trocar device that is releasably attached to the spacer, to enable implantation and selective positioning of the spacer by the surgeon from the posterior side of the spine, without the need to retract the dural nerve or the posterior longitudinal ligament.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] Not Applicable.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

[0002] Not Applicable.

BACKGROUND OF THE INVENTION

[0003] 1. The Field of the Invention

[0004] The present invention relates generally to an intervertebralspacer, and more particularly, but not necessarily entirely, to ainterbody spacing system for accomplishing enhanced intervertebralfusion between adjacent vertebral bodies of a human spine.

[0005] 2. Description of Related Art

[0006] The human spine is a complex, sophisticated mechanical system.The vertebrate spine operates as a structural member, providingstructural support for the other body parts. A normal human spine issegmented with seven cervical, twelve thoracic and five lumbar segments.The lumbar portion of the spine resides on the sacrum, which is attachedto the pelvis. The pelvis is supported by the hips and leg bones. Thebony vertebral bodies of the spine are separated by intervertebraldiscs, which reside sandwiched between the vertebral bodies and operateas joints allowing known degrees of flexion, extension, lateral bendingand axial rotation.

[0007] The intervertebral disc primarily serves as a mechanical cushionbetween adjacent vertebral bodies, and permits controlled motions withinvertebral segments of the axial skeleton. The disc is a multi-elementsystem, having three basic components: the nucleus pulposus (“nucleus”),the anulus fibrosus (“anulus”) and two vertebral end plates. The endplates are made of thin cartilage overlying a thin layer of hard,cortical bone that attaches to the spongy, richly vascular, cancellousbone of the vertebral body. The plates thereby operate to attachadjacent vertebrae to the disc. In other words, a transitional zone iscreated by the end plates between the malleable disc and the bonyvertebrae.

[0008] The anulus of the disc forms the disc perimeter, and is a tough,outer fibrous ring that binds adjacent vertebrae together. The fiberlayers of the anulus include fifteen to twenty overlapping plies, whichare inserted into the superior and inferior vertebral bodies at roughlya 40 degree angle in both directions. This causes bi-directionaltorsional resistance, as about half of the angulated fibers will tightenwhen the vertebrae rotate in either direction.

[0009] It is common practice to remove a spinal disc in cases of spinaldisc deterioration, disease or spinal injury. The discs sometimes becomediseased or damaged such that the intervertebral separation is reduced.Such events cause the height of the disc nucleus to decrease, which inturn causes the anulus to buckle in areas where the laminated plies areloosely bonded. As the overlapping laminated plies of the anulus beginto buckle and separate, either circumferential or radial anular tearsmay occur. Such disruption to the natural intervertebral separationproduces pain, which can be alleviated by removal of the disc andmaintenance of the natural separation distance. In cases of chronic backpain resulting from a degenerated or herniated disc, removal of the discbecomes medically necessary.

[0010] In some cases, the damaged disc may be replaced with a discprosthesis intended to duplicate the function of the natural spinaldisc. U.S. Pat. No. 4,863,477 (granted Sep. 5, 1989 to Monson) disclosesa resilient spinal disc prosthesis intended to replace the resiliency ofa natural human spinal disc. U.S. Pat. No. 5,192,326 (granted Mar. 9,1993 to Bao et al.) teaches a prosthetic nucleus for replacing just thenucleus portion of a human spinal disc.

[0011] In other cases it is desired to fuse the adjacent vertebraetogether after removal of the disc, sometimes referred to as“intervertebral fusion” or “interbody fusion.”

[0012] In cases of intervertebral fusion, it is known to position aspacer centrally within the space where the spinal disc once resided, orto position multiple spacers within that space. Such practices arecharacterized by certain disadvantages, including a disruption in thenatural curvature of the spine. For example, the vertebrae in the lower“lumbar” region of the spine reside in an arch referred to in themedical field as having a sagittal alignment. The sagittal alignment iscompromised when adjacent vertebral bodies that were once angled towardeach other on their posterior side become fused in a different, lessangled orientation relative to one another.

[0013] Another disadvantage of known spacing techniques andintervertebral spacers are the additional surgical complications thatarise in the use of multiple spacers in a single disc space. In suchcases, surgeons will often first perform a posterior surgery to removethe affected disc and affix posterior instrumentation to the posteriorside of the vertebrae to hold the posterior portions of the vertebrae ina desired position. Placement of the multiple spacers is often toodifficult to accomplish from the posterior side of the patient, at leastwithout causing with undue trauma to the patient, because a surgeonwould need to retract the dura nerve as well as the anteriorlongitudinal ligament, thereby increasing damage, pain and morbidity tothe patient. Surgeons have therefore often chosen to turn the patientover after completing the posterior surgical portion, to perform ananterior operative procedure, through the patient's belly, in order toinsert multiple spacers between the vertebrae from the anterior sideinstead of from the posterior side.

[0014] U.S. Pat. No. 5,961,554 (granted Oct. 5, 1999 to Janson et al.)illustrates a spacer having a high degree of porosity throughout, forenhanced tissue ingrowth characteristics. This patent does not addressthe problem of compromising the sagittal alignment, or of increased painand trauma to the patient by implantation of multiple spacers in asingle disk space.

[0015] The prior art is thus characterized by several disadvantages thatare addressed by the present invention. The present invention minimizes,and in some aspects eliminates, the above-mentioned failures, and otherproblems, by utilizing the methods and structural features describedherein.

BRIEF SUMMARY AND OBJECTS OF THE INVENTION

[0016] It is therefore an object of the present invention to provide anintervertebral spacing system that does not require an additional,anterior surgical procedure.

[0017] It is another object of the present invention, in accordance withone aspect thereof, to provide such an intervertebral spacing system bywhich sagittal alignment of the spine is restored.

[0018] It is a further object of the present invention, in accordancewith one aspect thereof, to provide such an intervertebral spacingsystem that can accommodate a larger host-graft interface betweenadjacent vertebral bodies.

[0019] It is an additional object of the present invention, inaccordance with one aspect thereof, to provide such an intervertebralspacing system in which bone grafting material is loaded in compressionbetween adjacent vertebral bodies of the spine.

[0020] It is yet another object of the present invention, in accordancewith one aspect thereof, to provide such an intervertebral spacingsystem that does not require retraction of the dural nerve, or of theanterior or posterior longitudinal ligaments, for implantation of thespacer.

[0021] The above objects and others not specifically recited arerealized in a specific illustrative embodiment of an intervertebralspacer adapted for implanting between adjacent vertebral bodies of ahuman spine as a load-bearing replacement for a spinal disc. The spacingmember includes an external, non-porous, concavo-convex contour withrespect to one dimension of said spacing member. The spacing member ispreferably constructed from a rigid, non-resilient load-bearing materialthat is incapable of elastic deformation. The spacing member is insertedwith the aid of a sheathed trocar device that is releasably attached tothe spacer, to enable implantation and selective positioning of thespacer by the surgeon from the posterior side of the spine, without theneed to retract the dural nerve or the posterior longitudinal ligament.

[0022] Additional objects and advantages of the invention will be setforth in the description which follows, and in part will be apparentfrom the description, or may be learned by the practice of the inventionwithout undue experimentation. The objects and advantages of theinvention may be realized and obtained by means of the instruments andcombinations particularly pointed out in the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] The above and other objects, features and advantages of theinvention will become apparent from a consideration of the subsequentdetailed description presented in connection with the accompanyingdrawings in which:

[0024]FIG. 1 is a perspective view of an intervertebral spacer, made inaccordance with the principles of the present invention;

[0025]FIG. 2 is a plan view of the intervertebral spacer of FIG. 1;

[0026]FIG. 3 is a frontal view of the intervertebral spacer of FIGS. 1and 2;

[0027]FIG. 4 is a side view of the intervertebral spacer of FIGS. 1, 2and 3;

[0028]FIG. 5 is side view of a pair of adjacent vertebral bodies fromthe lumbar region of a human spine;

[0029]FIG. 6 is a schematic view of a sheathed trocar device releasablyattached to a trial spacer shaped similarly to the intervertebral spacerof FIG. 1, in accordance with the principles of the present invention;

[0030]FIG. 7 is a schematic view of a sheathed trocar device releasablyattached to the intervertebral spacer of FIG. 1, in accordance with theprinciples of the present invention;

[0031] FIGS. 8A-8D illustrate a schematic progression of the placementof the intervertebral spacer of FIG. 1 between vertebral bodies of ahuman spine; and

[0032]FIG. 9 illustrates posterior instrumentation by which compressionis applied to the posterior sides of a paid of adjacenet vertebralbodies of a human spine.

DETAILED DESCRIPTION OF THE INVENTION

[0033] For the purposes of promoting an understanding of the principlesin accordance with the invention, reference will now be made to theembodiments illustrated in the drawings and specific language will beused to describe the same. It will nevertheless be understood that nolimitation of the scope of the invention is thereby intended. Anyalterations and further modifications of the inventive featuresillustrated herein, and any additional applications of the principles ofthe invention as illustrated herein, which would normally occur to oneskilled in the relevant art and having possession of this disclosure,are to be considered within the scope of the invention claimed.

[0034] Before the apparatus and methods of the present invention aredescribed further, it is to be understood that the invention is notlimited to the particular configurations, process steps, and materialsdisclosed herein as such configurations, process steps, and materialsmay vary somewhat. It is also to be understood that the terminologyemployed herein is used for the purpose of describing particularembodiments of the invention only, and is not intended to be limitingsince the scope of the present invention will be limited only by theappended claims and equivalents thereof.

[0035] The publications and other reference materials referred to hereinto describe the background of the invention and to provide additionaldetail regarding its practice are hereby incorporated by reference. Thereferences discussed herein are provided solely for their disclosureprior to the filing date of the present application. Nothing herein isto be construed as a suggestion or admission that the inventors are notentitled to antedate such disclosure by virtue of prior invention.

[0036] In describing and claiming the present invention, the followingterminology will be used in accordance with the definitions set outbelow.

[0037] As used herein, “comprising,” “including,” “containing,”“characterized by,” and grammatical equivalents thereof are inclusive oropen-ended terms that do not exclude additional, unrecited elements ormethod steps.

[0038] Applicants have discovered that several of the disadvantages ofthe prior art spinal disc replacement systems can be minimized, or eveneliminated, by the use of a cashew-shaped interbody spacer having atapered external shape, placing it is far anteriorly as possible betweenadjacent vertebral bodies, filling in the remaining posterior space withbone graft material, and applying compression to posterior portions ofthe vertebral bodies to load the bone graft in compression and restoresagittal alignment.

[0039] Referring now to FIGS. 1-4, there is shown a spacing member,referred to also herein as an intervertebral spacer or an interbodyspacer, designated generally at 10.

[0040] Briefly stated, the spacer 10 is utilized, along with autogenousbone grafting material, to replace a diseased or damaged spinal disc.Referring now to FIGS. 5-7, the procedure is implemented by making anincision 32 in the anulus 34 connecting adjacent vertebral bodies 31.The spinal disc (not shown) is surgically removed from the incision 32,after which the spacer 10 is placed through the incision 32 intoposition between the vertebral bodies 31. The spacer is preferablyplaced with its convex, anterior sidewall 12 facing anteriorly, and withits concave, posterior sidewall 14 facing posteriorly. Bone graftingmaterial is placed through the incision 32 to reside behind the spacer10, after which posterior instrumentation is attached to pedicle areas34 to force the vertebral bodies 31 together in compression, asillustrated schematically in FIG. 8D and more particularly in FIG. 9.

[0041] The unique aspects and procedures relating to the spacer 10 willnow be explained in more detail. Some of the key features of theinvention comprise the size, shape and placement of spacer 10. Thespacer 10 is preferably made of titanium, thus having a non-porousquality with a preferably smooth finish. The spacer 10 could also bemade of ceramic, or any other suitable material that is inert andbiologically compatible. The spacer 10 is thus constructed from a rigid,non-resilient load-bearing material, one that is preferably incapable ofelastic deformation. The spacer 10, by its anterior, convex sidewall 12and its posterior, concave sidewall 14, has thereby a concavo-convexcontour with respect to one dimension.

[0042] It is to be understood that the concept of an object having aconcavo-convex contour with respect to one dimension of the object, asreferred to herein, shall not require the concave and convex sides ofthe object to be parallel to one another, although such is preferred.The concept does however refer to a dimension in which the concave andconvex sides of the object are at least partially facing the directionof that dimension, as indicated by the dimension 16 of FIG. 1 inrelation to the spacer 10. It is also to be understood that the conceptof an object being concavo-convex in a single dimension shall therebyinclude an object that has concave and convex sides 14 and 12 in ahorizontal dimension 16, even though those very same sides are linear ina vertical dimension 20 at all points, such as in the case of the spacer10 shown in FIG. 1. For example, the spacer 10 is concavo-convex in theanterior-posterior direction 16, though not in a medial-lateraldirection 18 or vertical direction 20.

[0043] The upper surface 22 of the spacer 10 is preferably a planer,discontinuous surface having a plurality of spaced-apart elongaterecesses 24, with preferably a corner point 28 whereby one side 26 ofthe spacer 10 begins tapering in the medial-lateral direction 18, asshown most clearly in FIG. 3. The primary taper of the spacer 10 occursin the anterio-to-posterior direction 16, in that the spacer 10 narrowsin thickness in a continuous manner along substantially the entirespacer 10 as shown most clearly in FIG. 4. The upper surface 22 andlower surface 30 form an acute angle relative to a horizontal plane 23,the angle being with a range of preferably two to eight degrees, mostpreferably four degrees. The entire taper is therefore most preferablyan eight degree total taper, with four degrees of taper resulting fromthe upper surface 22 and the other four degrees of taper resulting fromthe lower surface 30.

[0044] As shown most clearly in FIG. 2, the spacer 10 has an arc-lengthAL that is preferably 1.218 inches, a width W that is preferably 0.320inches, a depth D that is preferably 0.532 inches, an inner radius R₂that is 0.271 inches, an outer radius R₁ that is preferably 0.591inches, and side radii R₃ and R₄ that are each preferably 0.160 inches.

[0045] The anterior, convex sidewall 12 and the posterior, concavesidewall 14 of the spacer 10 are each preferably linear in the verticaldimension 20, and are most preferably parallel relative to one another.

[0046] The primary goal in intervertebral fusion are immobilization ofthe affected vertebrae, restoration of the spinal disc space andsagittal alignment, and to provide an environment for bony fusionbetween vertebral bodies. Applicants have discovered that these goalsare most effectively accomplished by the mechanical principle of acantilever. Using the spacer 10 as a compression point, a cantilever isconstructed within the disc space as shown most clearly in FIG. 8D. Theprocedure for accomplishing this is as follows.

[0047]FIG. 8A is a schematic side, internal view of the vertebral bodies31 indicated in FIG. 5. The spinal disc 33 resides between the vertebralbodies 31, all of which reside between the anterior longitudinalligament (ALL) 36 and the posterior longitudinal ligament (PLL) 38. Thedural nerve (Dura) 40 resides posteriorly to the vertebral bodies 31 andthe PLL 38.

[0048] Referring now to FIG. 8B and FIG. 9, posterior access to thespine of the patient (not shown) is accomplished. Posteriorinstrumentation, preferably pedicle screws 42 (FIG. 9), are affixed toposterior pedicle portions 34 of the vertebral bodies 31. The associatedrods 44 and structure interconnecting the rods 44 with the pediclescrews 42 are not affixed until later on in the procedure. A posteriorportion of the lower vertebral body involved in the fusion, namely, theleft inferior articular facet, is removed and saved for futureautogenous bone grafting. A lamina spreader (not shown, but indicated inFIGS. 8B and 8C), is placed between the spinous processes 35 (shown inFIG. 5), and is operated to spread the adjacent vertebral bodies 31apart. The anterior longitudinal ligament 36 and posterior longitudinalligament 38 are left intact and need not be retracted.

[0049] After coagulation of the veins (not shown), the incision 32 (FIG.5) is made, preferably with a #15 scalpel, or any suitable surgicalinstrument, in a side section of the anulus 37. The disc 33 is thendetached from the vertebral end plates (not shown) with the propersurgical instrumentation, and is removed through the incision 32. Careis taken not to violate the bony vertebral end plate, which would causeexcessive bleeding and compromise the resistance to axial load when thespacer 10 is inserted.

[0050] When as much disc material has been removed as can safely beaccomplished, a trial spacer 50 is used to determine the correct spacersize. The trial spacer 50 preferably has the same shape as the spacer10, both of which are part of a set having various sizes, except thatthe trial spacer 50 does not include the recesses 24. The trial spacer50 is inserted into the incision 32 with a sheathed trocar device 52.The main purpose of trial spacer 50 is to evaluate a snugness of fit ofsaid trial spacer 50 as it resides between the adjacent vertebral bodies31, which enables the surgeon to determine a spacer size thereby. Thetrial spacer 50 may also have sharp edging, and is useable to clear awayany remaining unwanted tissue.

[0051] When the spacer size has been determined, a bone graft isprepared, preferably autogenous bone graft material 54 as shown in FIG.8C. Care is taken to remove all soft tissue from the autogenous bone,which will facilitate successful osseointegration of the graft.Additional bone can also be harvested from the spinous processes 35. Theharvested autogenous bone is then passed through a bone mill (not shown)to form suitable bone grafting material as known and understood to thosehaving ordinary skill in the art.

[0052] The spacer 10 is inserted through the incision 32 with thesheathed trocar device 52. The sheathed trocar device 52 includes atrocar rod 56 preferably slidably disposed within a hollow sheath 58.The trocar rod 56 and the hollow sheath 58 may moveably engaged witheach other in any suitable manner.

[0053] Both the trial spacer 50 and the spacer 10 preferably include afemale-threaded opening 50 a and 10 a formed therein, respectively, inwhich a male-threaded portion 57 of the trocar rod 56 may be releasablyinserted. The trocar rod 56 may of course be releasably attached to thetrial spacer 50 and spacer 10 in any other suitable manner. The trocarrod 56 has a longer length than the sheath member 58, such that aproximal portion 60 of the trocar rod 56 protrudes from the sheathmember 58 when the trocar rod 56 is attached to the trial spacer 50 orthe spacer 10.

[0054] The sheathed trocar device 52 accordingly provides an efficientlystabilized, releasable connection with the spacer 10. With the trocarrod 56 being attached directly to the spacer 10, the sheath member 58provides additional support by abutting up against the spacer andcontactably circumscribing the point of the attachment of the trocar rod56 with the spacer 10, thereby providing additional stability andcontrol over the positioning of the spacer 10.

[0055] The surgeon then selectively positions the spacer 10 within thespace residing between the adjacent vertebral bodies 31, preferably asfar anteriorly as possible and most preferably such that the spacer 10resides in contact with the anterior longitudinal ligament 36.

[0056] With the spacer 10 in place, the bone grafting material 54 isplaced through the incision 32 and into position between the adjacentvertebral bodies 31, such that said bone grafting material 54 residesposteriorly to the concave sidewall 14 of the spacer 10, and thusbetween the sidewall 14 and the posterior longitudinal ligament 38. Abone funnel (not shown) as known to those having ordinary skill in thefield may be used to funnel morselized bone grafting material into theincision 32.

[0057] It is noted that the concavo-convex shape of the spacer 10, andthe method of implantation with the spacer 10 residing as far anteriorlyas possible, operates to provide a larger bone-graft interface betweenthe adjacent vertebral bodies 31.

[0058] Referring now to FIG. 8D and FIG. 9, the lamina spreader isremoved and the pedicle screws 42 are interconnected with the rods 44 asknown in the field. Mild compression is applied by a compressioninstrument 46 to thereby slide rods 44 downwardly, after which thepedicle screws 42 are tightened to hold the rods 44 in place andmaintain the compression. Further compression is applied as desired,with the result being illustrated schematically in FIG. 8D. The bonegrafting material 54 is thereby loaded in compression by the posteriorlycompressed adjacent vertebral bodies 31 as shown. After final inspectionof the placement of the bone grafting material 54, routine closure ofthe wound is completed. The use of drains may be made at the discretionof the surgeon.

[0059] The spacer 10 thus operates to cause the adjacent vertebralbodies 31 to be suspended in the manner of a cantilever. The posteriorcompression provided by the pedicle screws 42 and rods 44, which mayalternatively be provided by any other suitable holding structure,causes the adjacent vertebral bodies 31 to be brought closer together ontheir posterior side than on their anterior side, consistent with thenatural sagittal alignment in which they were originally positioned, asunderstood by those having ordinary skill in the field.

[0060] It will be appreciated that the structure and apparatus of thetrocar rod 56 and sheath 58 constitute a positioning means for enablinga surgeon to adjust a position of the spacer 10 when the spacer 10resides between the adjacent intervertebral bodies 31. That structure ismerely one example of a means for positioning the spacer 10, and itshould be appreciated that any structure, apparatus or system forpositioning which performs functions that are the same as, or equivalentto, those disclosed herein are intended to fall within the scope of ameans for positioning, including those structures, apparatus or systemsfor positioning which are presently known, or which may become availablein the future. Anything which functions the same as, or equivalently to,a means for positioning falls within the scope of this element.

[0061] In accordance with the features and combinations described above,a preferred method of implanting an artificial intervertebral discincludes:

[0062] (a) making an incision in an anulus of a human spinal columnbetween adjacent vertebral bodies of said spinal column to therebyexpose a space residing between said adjacent vertebral bodies;

[0063] (b) inserting a spacing member through the incision and intoposition between the adjacent vertebral bodies, and positioning saidspacing member at an anterior location with respect to the spinal columnsuch that more intervertebral space resides posteriorly to said spacingmember than anteriorly thereto;

[0064] (c) applying compression to posterior portions of the adjacentvertebral bodies.

[0065] It is to be understood that the above-described arrangements areonly illustrative of the application of the principles of the presentinvention. Numerous modifications and alternative arrangements may bedevised by those skilled in the art without departing from the spiritand scope of the present invention and the appended are intended tocover such modifications and arrangements. Thus, while the presentinvention has been shown in the drawings and fully described above withparticularity and detail in connection with what is presently deemed tobe the most practical and preferred embodiment(s) of the invention, itwill be apparent to those of ordinary skill in the art that numerousmodifications, including, but not limited to, variations in size,materials, shape, form, function and manner of operation, assembly anduse may be made without departing from the principles and concepts setforth herein.

What is claimed is:
 1. An intervertebral spacing implant comprising: aspacing member adapted for implanting between adjacent vertebral bodiesof a human spine as a load-bearing replacement for a spinal disc, saidspacing member further comprising an external, non-porous,concavo-convex contour with respect to one dimension of said spacingmember.
 2. The intervertebral spacing implant of claim 1, wherein thespacing member is constructed from a rigid, non-resilient load-bearingmaterial that is incapable of elastic deformation.
 3. The intervertebralspacing implant of claim 2, wherein the spacing member comprises metal.4. The intervertebral spacing implant of claim 3, wherein the spacingmember comprises titanium.
 5. The intervertebral spacing implant ofclaim 2, wherein the spacing member comprises ceramic.
 6. Theintervertebral spacing implant of claim 1, wherein the spacing memberincludes an anterior wall and a posterior wall, and wherein the externalconcavo-convex contour of the spacer is defined by the posterior wallbeing concave in a horizontal dimension and by the anterior wall beingconvex in a horizontal dimension.
 7. The intervertebral spacing implantof claim 6, wherein the anterior wall and the posterior wall of thespacing member are each linear in a vertical dimension.
 8. Theintervertebral spacing implant of claim 7, wherein the concavo-convexcontour comprises a concave posterior side, and a convex anterior sidedisposed in a substantial parallel orientation with respect to theconcave posterior side.
 9. The intervertebral spacing implant of claim1, wherein the spacing member defines an imaginary arcuate centerlineresiding between opposing sides of the external concavo-convex contourof said spacing member to thereby enable said spacing member to beinserted thorough an incision along an arcuate insertion path.
 10. Theintervertebral spacing implant of claim 9, wherein the spacing member isconfigured and adapted to be inserted along said arcuate movement pathin a manner such that said arcuate movement path coincides with theimaginary arcuate centerline of said spacing member.
 11. Theintervertebral spacing implant of claim 1, wherein the spacing memberfurther comprises a disc-like member having a thickness, and a lengththat is greater in length than said thickness, and a width that isgreater in width than said thickness.
 12. The intervertebral spacingimplant of claim 11, wherein the thickness of the spacing member isdefined by a perimeter wall that constitutes the concave side and theconvex side of the external concavo-convex contour of said spacingmember.
 13. The intervertebral spacing implant of claim 1, wherein thespacing member further comprises un upper side having a plurality ofspaced-apart recesses formed therein.
 14. The intervertebral spacingimplant of claim 13, wherein the recesses are elongate and are disposedin a substantial parallel orientation with respect to each other.
 15. Anintervertebral spacing implant comprising: a spacing member adapted forimplanting between adjacent vertebral bodies of a human spine as aload-bearing replacement for a spinal disc, said spacing member furthercomprising a non-porous body having a tapered external shape such thatsaid spacing member narrows in thickness in a first direction.
 16. Theintervertebral spacing implant of claim 15, said spacing member having adiscontinuous upper surface.
 17. The intervertebral spacing implant ofclaim 15, wherein the tapered external shape of said spacing membernarrows in thickness in a continuous manner along a majority width ofsaid spacing member in an anterior-to-posterior direction.
 18. Theintervertebral spacing implant of claim 17, wherein the spacing memberinclude an upper surface that forms an acute angle with respect to ahorizontal plan, said acute angle being in a range of two to sixdegrees.
 19. The intervertebral spacing implant of claim 18, the spacingmember having a discontinuous upper surface.
 20. The intervertebralspacing implant of claim 19, wherein the upper surface includes aplurality of elongate recesses formed therein, said recesses extendingin an anterior-to-posterior direction.
 21. The intervertebral spacingimplant of claim 18, wherein the spacing member includes a lower surfacethat forms an acute angle with respect to a horizontal plan, said acuteangle being in a range of approximately two degrees to eight degrees.22. The intervertebral spacing implant of claim 21, wherein the upperand lower surface of the spacing member each form a continuous acuteangle of approximately four degrees with respect to a horizontal plane,for a total continuous taper of approximately eight degrees.
 23. Theintervertebral spacing implant of claim 15, wherein said spacing memberfurther comprises a convex side, and wherein the tapered external shapeof said spacing member is adapted such that said spacing member narrowsin thickness in an anterior-to-posterior direction when implanted withsaid convex side facing an anterior direction.
 24. The intervertebralspacing implant of claim 23, wherein the spacing member furthercomprises an upper surface, and wherein the tapered external shape ofthe spacing member is such that the upper surface of said spacing memberdefines a first acute angle with respect to a plane that is orthogonalto the convex side of the spacing member.
 25. The intervertebral spacingimplant of claim 15, wherein the tapered external shape of said spacingmember comprises a taper sufficient in degree to permit a lordosisspinal configuration to be restored when said spacing member issandwiched between adjacent intervertebral bodies.
 26. An intervertebralspacing implant system comprising: a spacing member adapted forimplanting between adjacent intervertebral bodies of a human spine;positioning means for enabling a surgeon to adjust a position of thespacing member when said spacing member resides between adjacentintervertebral bodies, said positioning means comprising a sheathmember, a rod member slidably insertable into the sheath member, and ameans for releasably attaching the rod member to the spacing member. 27.The intervertebral spacing implant system of claim 26, wherein the rodmember has a longer length than the sheath member, such that a proximalportion of the rod member protrudes from the sheath member when said rodmember resides within said sheath member and is attached to the spacingmember.
 28. The intervertebral spacing implant system of claim 26,wherein the means for releasably attaching the rod member to the spacingmember further comprises a threaded engagement.
 29. The intervertebralspacing implant system of claim 28, wherein the means for releasablyattaching the rod member to the spacing member further comprises afemale threaded recess formed in the spacing member, and wherein the rodmember comprises a male threaded distal end having a size andconfiguration sufficient to permit threaded engagement between said malethreaded distal end of the rod member and the female threaded recessformed in the spacing member.
 30. An intervertebral spacing implantsystem comprising: a spacing member adapted for implanting betweenadjacent intervertebral bodies of a human spine; positioning means forenabling a surgeon to adjust a position of the spacing member when saidspacing member resides between adjacent intervertebral bodies, saidpositioning means further comprising an attachment means for becomingreleasably attached to the spacing member at a first area of attachment,and a stabilizing means for removably contacting the spacing memberalong a contact line that surrounds the first area of attachment. 31.The intervertebral spacing implant system of claim 30, wherein thestabilizing means further comprises means for contacting the spacingmember along a circular contact line that circumscribes the first areaof attachment, said circular contact line being disposed in asubstantially co-axial orientation with respect to the first area ofattachment.
 32. A method of implanting an artificial intervertebral disccomprising: (a) making an incision in an anulus of a human spinal columnbetween adjacent vertebral bodies of said spinal column to therebyexpose a space residing between said adjacent vertebral bodies; (b)inserting a spacing member through the incision and into positionbetween the adjacent vertebral bodies, and positioning said spacingmember at an anterior location with respect to the spinal column suchthat more intervertebral space resides posteriorly to said spacingmember than anteriorly thereto; (c) applying compression to posteriorportions of the adjacent vertebral bodies.
 33. The method of claim 32,further comprising: (d) removing a natural human disc from the space,prior to part (b).
 34. The method of claim 32, wherein part (c) furthercomprises compressing the posterior portions of the adjacent vertebralbodies toward each other to a degree sufficient to move said adjacentvertebral bodies into a sagittal alignment.
 35. The method of claim 34,further comprising: (e) attaching a holding means to the adjacentvertebral bodies for holding said adjacent vertebral bodies in thesagittal alignment to thereby inhibit said vertebral bodies from movingout of sagittal alignment.
 36. The method of claim 32, wherein part (b)further comprises positioning the spacing member sufficiently anteriorlysuch that said spacing member resides in contact with an anteriorlongitudinal ligament of the spinal column.
 37. A method of implantingan artificial intervertebral disc comprising: (a) making an incision inan anulus of a human spinal column between adjacent vertebral bodies ofsaid spinal column to thereby expose a space residing between saidadjacent vertebral bodies; (b) inserting a spacing member through theincision and into position between the adjacent vertebral bodies, andpositioning said spacing member at an anterior location with respect tothe spinal column such that more intervertebral space residesposteriorly to said spacing member than anteriorly thereto; (c) placingbone grafting material through the incision and into position betweenthe adjacent vertebral bodies such that said bone grafting materialresides between the spacing member and a posterior longitudinal ligamentof the spinal column; and (d) attaching a compression means to posteriorportions of the adjacent vertebral bodies to thereby force saidposterior portions of the adjacent vertebral bodies toward each otherand thereby compress the bone grafting material, said compression meanscomprising pedicle screws and rod members intercoupling said screws. 38.The method of claim 37, wherein the bone grafting material comprisesautogenous bone.
 39. A method of implanting an artificial intervertebraldisc comprising: (a) inserting a spacing member into position betweenadjacent vertebral bodies of a human spinal column, and positioning saidspacing member at an anterior location with respect to the spinal columnsuch that more intervertebral space resides posteriorly to said spacingmember than anteriorly thereto; and (b) applying compression toposterior portions of the adjacent vertebral bodies.
 40. The method ofclaim 39, further comprising additional parts to be performed prior topart (b), said additional parts comprising: (i) placing bone graftingmaterial into position between the adjacent vertebral bodies such thatsaid bone grafting material resides between the spacing member and aposterior longitudinal ligament of the spinal column; and (ii) attachinga compression means to posterior portions of the adjacent vertebralbodies to thereby force said posterior portions of the adjacentvertebral bodies toward each other and thereby compress the bonegrafting material, said compression means comprising pedicle screws androd members intercoupling said screws.
 41. A method of implanting anartificial intervertebral disc comprising: (a) making an incision in ananulus of a human spinal column between adjacent vertebral bodies ofsaid spinal column to thereby expose a space residing between saidadjacent vertebral bodies; (b) selecting a spacing member comprising anexternal concavo-convex contour with respect to one dimension of saidspacing member, wherein the spacing member defines an imaginary arcuatecenterline residing between opposing sides of the externalconcavo-convex contour of said spacing member; (c) inserting the spacingmember along an arcuate insertion path through the incision such thatthe imaginary arcuate centerline follows said arcuate insertion pathduring the insertion.
 42. A method of implanting an artificialintervertebral disc comprising: (a) making an incision in an anulus of ahuman spinal column between adjacent vertebral bodies of said spinalcolumn to thereby expose a space residing between said adjacentvertebral bodies; (b) inserting a trial spacer through the incision andinto position between the adjacent vertebral bodies, and evaluating asnugness of fit of said spacer as it resides between said adjacentvertebral bodies and determining a spacer size thereby; (c) selecting aspacing member having the spacer size determined in part (b) andinserting said spacing member through the incision and into positionbetween the adjacent vertebral bodies.
 43. The method of claim 42,wherein part (b) further comprises dislodging any unwanted soft tissuefrom between the vertebral bodies with the trial spacer.